Facebook allows outsiders to add functionality to the site but reserves the right to change that policy at any time, to charge a fee for applications, or to de-emphasize or eliminate apps that court controversy or that they simply don't like.

The ability to make new work from old work - especially if that new work is different enough that it doesn't dent the market for the old work - is something that benefits all creators, since so few can claim not to have a giant or 10 supporting them underneath.

With the rise of software patents, engineers coding new stuff - whether within a large software company or as kids writing smartphone apps - are exposed to a claim that somewhere a prior patent is being infringed.

Jonathan Zittrain Quotes